Summary of Work: We have shown in a number of previous studies that inhibition of the CD11/18 adhesion complex on neutrophils worsens infection and outcome in bacteria-challenged animal models of sepsis. Although this complex is associated in some models with inflammatory tissue injury, our experience has suggested that stimulation of this complex might have beneficial effects in some cases of infection and sepsis. SK 107647 is a synthetic peptide that has been shown in both small and large animal models to stimulate neutrophil expression of CD11b without increasing circulating neutrophil counts. We are presently designing a three-part study that will evaluate the effects of SK 107647 in a canine model of peritonitis. We have shown in initial studies that it is possible to reliably measure CD11b expression in this model. In subsequent studies, we will determine the effects of SK 107647 on neutrophil CD11b expression in the model. If The agent does stimulate canine CD11b expression and is not associated with toxicity, we will then test it in the canine peritonitis model.